Trap success for Merriam's shrews is relatively low. For example, in a study done over a seven-year period, only eight Merriam's shrews were captured. It is difficult to say whether this reflects low population levels, or just difficulty in trapping such a small animal. Inability to trap these animals is probably the reason little is known about the species.
There is little information available on how Merriam's shrews communicate with one another. However, we can infer that they use some chemical communication because of the sniffing that males do of females, probably to determine their reproductive condition. Also, glands on the flanks are pronounced, especially on males and especially during breeding season, indicating that there is some reproductive function of the scents they produce.
Further, as mammals, there is tactile communication. This typically occurs as part of mating, parental care, and during aggressive encounters with conspecifics. Caravanning of the young, which is common in shrews, could be considered a means of communicating where to go.
Most mammals have some accoustic communication, although the vocalizations of this species have not been described. Visual signals often occur in mammals, but are probably not terribly important to S. merriami, as they are nocturnal, solitary, and apparently don't see very well.
Communication Channels: tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
Because the species has not been thoroughly studied, the status of S. merriami is unknown. No special is status is listed according to the IUCN.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
There are no known adverse affects of S. merriami on humans.
The extent to which Merriam's shrews affect human populations is unknown. However, the species preys on insects, serving as a natural pest control.
Positive Impacts: controls pest population
Because they are so hard to trap, not much is known on the ecosystem role of Merriam's shrews. However, the species does eat a large quantity of insects, spiders, and earthworms, probably exerting some impact on their populations.
Due to their small body size, Merriam's shrews tend to lose a great amount of body heat. Thus, to make up for this lost energy, they spend a significant amount of time foraging for food. They often use the runways of various species of voles for foraging. They sometimes eat food equal to or greater than their body weight in 24 hours. Foods eaten include insects, earthworms, spiders, and sometimes small vertebrates.
Animal Foods: insects; terrestrial non-insect arthropods; terrestrial worms
Primary Diet: carnivore (Insectivore )
Merriam's shrews, Sorex merriami, range from north-central Washington south to Eastern California, down through Arizona to New Mexico. They range as far east as western Nebraska and North Dakota. A recent study discovered that the Merriam's shrews known geographic range has now expanded as far north as British Columbia in Canada.
Biogeographic Regions: nearctic (Native )
Merriam's shrews live in dry habitats compared to other species in the genus. They are found in areas with short-grass prairies and sagebrush.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: savanna or grassland
No information is available about the longevity of Merriam's shrews. Most shrews have an average life span of one year. However, since these animals don't become reproductive until they are about a year of age, we can assume that they probably live a bit longer.
Average lifespan
Status: wild: 1 years.
Merriam's shrews range in total length from 88 to 107 mm, with tail length ranging from 33 to 42 mm. They generally weigh between 4 and 7 g. The back is brown-gray or gray in color and the underside is white.
Merriam's shrews are often confused with masked shrews due to the similarity in size. Skull and tooth morphology are used to distinguish these two species. The skull of S. merriami is broader across the rostrum and the braincase when compared to that of masked shrews. Medial tines are absent on the first upper incisor, and the condylobasal length is approximately 15.9 mm. Another distinguishing feature of the dentition of S. merriami is that the third upper unicuspid tooth is larger than the fourth upper unicuspid.
Range mass: 4 to 7 g.
Range length: 88 to 107 mm.
Sexual Dimorphism: sexes alike
Other Physical Features: endothermic ; bilateral symmetry
The only known predators of S. merriami are owls. However, it is likely that nocturnal carnivores who are capable of catching these animals probably occasionally do. It is thought that the pungent scent of these shrews may inhibit predation to some extent.
Known Predators:
Information about reproduction in Merriam's shrews is minimal. In most shrews, mating behaviors are very elementary. A male typically chases a female with his nose close to her posterior. This allows the male to sniff (apparently to determine her reproductive condition) and mount the female when she stops running.
Not much is known about reproduction in Merriam's shrews. It is thought that the breeding season is from mid-March to July, and that females can breed twice in a given year. Gestation for most shrews is 24 to 30 days, with females having between 5 and 7 young per litter. The young are cared for until approximately 25 days, during which time they are completely dependent. Most shrews become sexually mature around 1 year of age. Rarely, some females will mate before five months of age.
Breeding interval: These shrews probably breed twice per year.
Breeding season: It is thought that Merriam's shrews breed from mid March to July.
Range number of offspring: 5 to 7.
Range gestation period: 24 to 30 days.
Range weaning age: 22 to 25 days.
Average time to independence: 25 days.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
For most shrews, the young are cared for by the mother until they are weened. Care includes provision of food (milk), protection, and grooming. Weening occurs between 22 and 25 days. After the young are weened, they are completely independent. Male parental care has not been reported.
Parental Investment: no parental involvement; altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)
